Honeywell 5-2 Day Programmable Thermostat. Weekday/Weekend Programming - One program for the weekdays and a separate program for the weekends with 4 program periods per day. Energy Savings - Program to save up to 33% on annual heating and cooling costs (if used as directed. Savings may vary depending on geographic region and usage). Easy to Use - Basic operation keeps programming easy. Precise temperature control of /-1 F to maximize comfort. Works with heating and cooling systems plus heat pumps without back-up heat. Does not work with heat pump systems with back-up heat, multi-stage heating/cooling systems and electric baseboard heat (120-240V). Works with low volt heating/cooling systems including millivolt & heat pumps without auxiliary heat; Easy to install; Backlit display.